The present invention is in the area of display technology, and pertains in particular to an electrophoretic display with high resolution and low power consumption using electrically-induced motion of charged display markers in a gelatinous base material to present a display.
The advent of portable personal computers, such as notebook and laptop computers, required, because of the form factors required, flat panel displays, and several sorts of flat-panel displays have been developed and marketed. Perhaps the two most successful types of such displays are liquid-crystal displays and plasma displays.
Flat-panel displays have been optimized for displaying color and motion, and for operation at low power levels, which is desirable for computers like laptops and notebooks that are, at least part of the time, operated from batteries. In this optimization light weight and resolution have been sacrificed. Flat panel displays optimized in this way typically have resolution of from 50-100 dots per inch (DPI) in each direction. In the case of color displays, because three color dots are needed for each pixel, resolution is even poorer.
There are technologies available which allow resolution as high as 2000 DPI, but the size of such displays is typically limited to fractions of an inch in each direction. Two important reasons for the resolution limits of flat panel displays are power consumption and refresh rate. Given a certain technology, active-matrix LCD for example, power consumption is a function of resolution because each pixel element consumes power. Given a specific screen size, doubling resolution (DPI) quadruples the number of pixels, and therefore quadruples power consumption. Also, increasing the number of pixels increases the amount of data needed to keep the overall display updated.
As an example, a computer display considered to be high resolution might have 1024xc3x97768 pixels, each in 3 colors, each addressed by eight bits, and refreshed approximately 70 times per second (70 Hz refresh rate). Such a system requires 165 Mbytes of data per second.
Consider now a small document with printed characters, like a newspaper, with a resolution of about 300 DPI. An 8 inch by 11 inch printed area of such a document represents a resolution of 2400xc3x973300 pixels (monochrome). Data rates in this situation are in excess of 550 Mbytes per second. Also, using any of the popular conventional technologies, such a display would be quite heavy and would consume considerable power.
What is needed is a new display technology, allowing ultra-light (by today""s standards), and ultra high-resolution displays, requiring a very low refresh rate and very low power consumption. It is to these ends that the present invention, described in detail below, is directed.
In a preferred embodiment of the present invention a display panel is provided comprising a first panel; a second panel spaced apart from the first panel, providing a volume therebetween; an open-celled, opaque gelatinous material having a first color in the volume between the panels; multiple ionic particles having a second color suspended in the gelatinous material; and a matrix of electrodes implemented between the two panels or on one of the two panels. Activating individual ones of the electrodes in the matrix causes groups of the multiple ionic particles to translate through the gelatinous material and collect against the first panel, forming a pattern of pixels of the second color against a background of the first color.
In some embodiments the first color is white and the second color is black. In others other colors may be used, with the preference that the colors be easily distinguishable from each other.
The matrix of electrodes in some embodiments comprises individual electrodes spaced in a Cartesian array on one of the two panels and a common electrode surface implemented on the other of the two panels. In these embodiments individual electrodes are formed in or on a polysilicon layer deposited on the one of the two panels, and circuitry for controlling activation of the electrodes is also formed on the one of the two panels. In other embodiments individual electrodes are formed by a first set of substantially parallel lines of transparent, electrically conductive material formed on one of the two panels, and a second set of substantially parallel lines of electrically conductive material at right angles to the first set of substantially parallel lines of transparent, electrically conductive material, the second set of lines separated from the first by means of a semi-conducting material. By exceeding the breakdown voltage between those lines, the immediate surroundings become conductive, and individual electrodes are formed at the intersections of individual lines on one panel These areas again act in attracting or repelling suspended ionic particles, resulting in formation of a visible pattern.
In preferred embodiments the display panel comprises a data port and control circuitry connected to the data port, the control circuitry adapted for addressing and activating individual electrodes according to a data stream received at the data port. Methods are provided for forming such displays.
A very big advantage for displays according to embodiments of the present invention is that these displays require power only when altering the displayed image. While a display is maintained, no power is required; that is, the image need not be refreshed. Displays according to embodiments of the present invention are thus especially suited for displaying pages of text, as the mean time between updates for such display can be expected to be. relatively long. Another big advantage, which accrues because of the low-voltage, low-power aspects of the unique technology used for embodiments of this invention, is that resolution may be substantially increased without increasing power requirements. High resolution is also posssible because the structure of devices according to embodiments of the present invention lends itself to small geometry, hence high resolution.